Biochemical nature of high-molecular-weight prolactin of human serum: identification of a prolactin-binding protein.
The biochemical nature of a high-molecular-weight immunoreactive prolactin (HMW-irPRL) prepared by gel filtration of women's sera with predominance of this hormone form was studied. Immunochemical characteristics of HMW-irPRL are different from those of 23 kD prolactin (23 kD-PRL). A protein which specifically and reversibly binds to human [125I]PRL is isolated from the pooled fractions of HMW-irPRL by affinity chromatography on prolactin-Sepharose. According to gel filtration, the binding protein (BP) has molecular weight about 150 kD, and it reversibly binds to protein A immobilized on Sepharose. Analysis of BP by SDS-PAGE resulted in two major protein bands, of 65-70 and approximately 150 kD. Both the bands, when transferred to nitrocellulose, interacted with [125I]protein A. Binding of highly purified human pituitary prolactin to the BP significantly decreased the immunoreactivity of the hormone. The molecular weight of BP and its interaction with protein A and recognition by poly- and monoclonal antibodies against human (but not guinea pig) IgG indicate that BP may be an immunoglobulin. Thus, our data demonstrate that HMW-irPRL is formed by the binding of 23 kD-PRL to a specific serum protein which is probably an anti-prolactin IgG.
Bulatov
A A
AA
Endocrinology Research Center, Russian Academy of Medical Sciences, Moscow, Russia.
Martynov
A V
AV
Smirnova
N B
NB
D000327:Adsorption; D002352:Carrier Proteins / Q000097:blood* / Q000302:isolation & purification; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D005260:Female; D006801:Humans; D008970:Molecular Weight; D011388:Prolactin / Q000097:blood*; D011863:Radioimmunoassay
D002352:Carrier Proteins; C029702:prolactin-binding protein; D011388:Prolactin